The present invention relates to a thin-film magnetic head provided with a magnetoresistive effect (MR) element such as an anisotropic magnetoresistive effect (AMR) element, with a giant magnetoresistive effect (GMR) element such as a spin-valve magnetoresistive effect (SVMR) element, or with a tunnel magnetoresistive effect (TMR) element.
Such an MR element has a sensor film operating as a sensor (an MR layer in the AMR element, a ferromagnetic free layer in the GMR element and the TMR element for example), two magnetic domain control films joined or contacted with side end faces of the sensor film, respectively, for applying a longitudinal bias to the sensor film in order to make this sensor film in a single domain state.
The magnetic domain control films are in general made of CoPt or CoCrPt for example. If necessary, a single layer under film of TiW, Cr or CrTi for example is formed under the magnetic domain control films. By using such an under film, it is possible to improve magnetic performance of the magnetic domain control films, such as for example a coercive force Hc and a rectangularity ratio indicating a residual magnetic flux density Br/a saturation magnetic flux density Bs.
However, even if such an under film is used, there is a limit in improvement in the magnetic performance of the magnetic domain control films. This is because the characteristic of the magnetic domain control films depends on the kind of a layer formed under the under film.
Particularly, in junction or joining regions between the sensor film and the magnetic domain control films of the MR element, since the sensor film including for example a NiFe layer and/or a Co layer exists under the under film, the magnetic performance of the magnetic domain control films will be spoiled remarkably. If the magnetic performance of the magnetic domain control films deteriorates, noise such as Barkhausen noise will frequently occur during operations of the magnetic head.
It is therefore an object of the present invention to provide a thin-film magnetic head with an MR element which will generate little noise and will have an outstanding output stability.
According to the present invention, a thin-film magnetic head with an MR element, includes an MR film, under films each having a multilayer structure with a first under layer and a second under layer laminated on the first under layer, and magnetic domain control films joined to side end faces of the MR film through the under films.
Since each under film of the magnetic domain control films has a multilayer structure including the first and second under layers laminated each other, the magnetic domain control films will not be influenced to deteriorate its magnetic domain control performance from a layer below the under film. As a result, the MR element can provide extremely stable output with suppressing occurrence of Barkhausen noise.
It is preferred that a thickness of the first under layer in joined sections of the MR film with the magnetic domain control films is 5 nm or less.
It is also preferred that the first under layer is made of Ta, Hf, Nb or Zr.
It is also preferred that the second under layer is made of TiW, Cr or CrTi.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.